In the constant current drive type driver used for an LVDS (low voltage differential signal) interface, the parasitic capacitance of the package pins is charged and discharged sufficiently at a high speed to secure the high speed signal transmission operation. Further, the AC differential amplitude large enough to be received by the receiver can be obtained. The driver circuit device comprises: a transmit circuit composed of transistors (52, 53, 56, 57) for transmitting a signal by switching the signal current direction flowing through a pair of transmission lines (8, 9) connected between two output terminals (13 and 13B); and a constant current source composed of transistors (54, 75) for controlling the current value of the transmit circuit. In the idle state, only one of the two transistors (54 and 75) of the constant current source is turned on to limit the signal current flowing through the output terminals (13 and 13B). On the other hand, in the high speed signal transmission, both the transistors (54, 75) are turned on to increase the signal current flowing through the output terminals (13, 13B) to obtain a signal current of high DC LVDS level.